lvm: Allow multiple LVs to be refreshed at once

lvm.refreshLV() function used to accept only single lv, requiring
multiple invocations for refreshing multiple lvs, although lvm allows
refreshing of multiple lvs. This patch rename the function and accept
multiple lvs and invoke lvchange once with given lvs.

This change is required for patch http://gerrit.ovirt.org/#/c/21501.

Change-Id: I1ecc64b8ca0133b030ba5bfa37f1a2c55067dd5d
Bug-Url: https://bugzilla.redhat.com/1009812
Signed-off-by: Lee Yarwood <lyarwood@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/19871
Reviewed-by: Nir Soffer <nsoffer@redhat.com>
Reviewed-by: Allon Mureinik <amureini@redhat.com>
Tested-by: Nir Soffer <nsoffer@redhat.com>
Reviewed-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/21500